It can be the that most of the commercial alumina is produced by the Bayer Process. It is also possible to produce hydrated alumina by other methods. Several other methods result in the inclusion of high levels of one or more impurities.
Low purity specialty alumina can be used as a refractory material (resistant to very high temperatures), as a ceramic and in the electrolytic production of aluminum metal.
However, for certain applications, high purity alumina (HPA) is required. Many synthetic precious stones have a high purity alumina base, including ruby, topaz and sapphire. These crystals are used mostly in jewelry, infrared, UV and laser optics, and as a high-end electronic substrate.
Half of the world's annual production of ultra-pure alumina goes into making synthetic sapphire for use in fiber optics and, more recently, in LED lighting for home and automotive markets. It is also used in the production of high-pressure sodium vapor lamp tubes and the manufacturing of video and computer equipment, as well as in metallographic polishing and the polishing of optic and electronic materials.
There is a growth in HPA annual worldwide demand, which according to certain market experts should rise from 9,000 tons in 2012 to over 15,000 tons in 2015. This should lead to a substantial supply deficit of about 6,000 tons per year caused notably by the global increase of light emitting diodes (LED) demand.
A number of methods for preparing high purity alumina have been proposed that start with pure aluminum metal, organoaluminum compounds or alums. These in general start with a high cost material or generate products not recyclable to the process when calcined and are therefore not applicable to commercial production.
There is thus a need for providing an alternative to the existing solutions for purifying aluminum ions and/or for preparing alumina that has a high purity.